1. Field of the Invention
The present invention relates to an organic electroluminescent structure and a method of making the same, and more particularly, to an organic electroluminescent structure having a luminescent and electron transport layer that has both effects of the organic luminescence and electron transport and a making method of an organic electroluminescent structure being able to reduce the number of shadow masks used for defining an organic luminescent layer.
2. Description of the Prior Art
Flat displays have advantages of saving electricity, low radiation, and small size over traditional cathode ray tube (CRT) displays. For these reasons, flat displays are replacing CRT displays gradually. With the improvements of flat display techniques, the price of flat displays is getting lower. Therefore, flat displays are more popular and undergoing developments for larger sizes. Because of having the advantages of high contrast and self-luminosity, the organic electroluminescence display is a most remarkable product among the flat displays at present.
Please refer to FIG. 1. FIG. 1 is a cross-sectional schematic diagram illustrating a conventional organic electroluminescent structure of a pixel region in an organic electroluminescent panel. As shown in FIG. 1, the conventional organic electroluminescent structure includes an anode 10, a hole injection layer 12 disposed on the anode 10, a hole transport layer 14 disposed on the hole injection layer 12, an organic luminescent matrix 16 disposed on the hole transport layer 14, an electron transport layer 18 disposed on the organic luminescent matrix 16, and a cathode 20 disposed on the electron transport layer 18.
In order to display a full color frame, the organic electroluminescent structure of any pixel region in the organic luminescent panel includes blue sub-pixel, a green sub-pixel and a red sub-pixel, and the organic electroluminescent matrix 16 includes a blue organic luminescent pattern 16B, a green organic luminescent pattern 16G and a red organic luminescent pattern 16R, wherein the blue organic luminescent pattern 16B is in charge of providing luminescence of the blue sub-pixel, the green organic luminescent pattern 16G is in charge of providing luminescence of the green sub-pixel, and the red organic luminescent pattern 16R is in charge of providing luminescence of the red sub-pixel so as to combine a beautiful full color frame.
An evaporation process combined with shadow masks is used to form the organic luminescent matrix 16, and for the organic luminescent matrix 16 of the conventional organic electroluminescent structure, the blue organic luminescent pattern 16B, the green organic luminescent pattern 16G and the red organic luminescent pattern 16R have to respectively use three shadow masks to perform evaporation. First, in the manufacturing process, because the alignment deviation will be generated unpreventably while using the shadow masks, the conventional making method for the organic luminescent matrix 16 of the organic electroluminescent structure has to use three shadow masks so as to increase a risk of alignment deviation. The alignment deviation of the organic luminescent matrix 16 will generate some problems, such as a shadow effect etc., so that the displaying quality is bad. In addition, when a size of the required organic electroluminescent panel is large, a large shadow mask should be used. The large shadow mask will easily generate a bending effect, and the pattern conversion of the organic luminescent matrix 16 also will generate deviation.
Therefore, to reduce the using number of shadow masks so as to prevent the disadvantages to the organic electroluminescent structure produced by alignment deviation is an important object in present research of the organic electroluminescent structure.